1. Field of the Invention:
This invention relates generally to particle counting systems for sensing and counting particles suspended in a sample fluid as said sample fluid is drawn through an orifice from a sample chamber to a substantially enclosed fluid passage, and specifically to a system for detecting leaks and clogs in such particle counting system, automatically removing detected clogs, and automatically testing to verify that the detected clogs have been removed.
2. Description of the Prior Art:
Particle counting systems are widely used for sensing and counting particles suspended in a sample fluid as the sample fluid is drawn through a tiny orifice from a sample chamber into a substantially enclosed fluid passage. In the medical field, particle counting systems are used to count both red and white blood cells. An electrode is placed on each side of the tiny orifice, and a constant DC current is directed through the orifice via the sample fluid. Red and white blood cells obstruct the DC current path as they pass through the orifice. The blood cells physical obstruction of the current path through the orifice results in a voltage pulse between the electrodes as blood cells are caused to pass through the orifice by hydraulic pressure. By counting the voltage pulses, one may indirectly count the number of blood cells passed through the orifice.
It is important to recognize that blood cell and other counts are only meaningful if they can accurately reflect the number of cells or particles per volumetric unit. Therefore, it is critical that a particle counting system be adapted to pass a selected amount of sample fluid through the orifice as desired--no more, no less. Leaks or clogs in the particle counting system will result n either under-counting or over-counting of blood cells or particles per unit volume.
It is widely known that organic sample fluids such as blood tend to coagulate or accumulate upon the surfaces with which it comes into contact. For example, in the blood cell counters, blood and other organic materials tend to accumulate at the orifice, or along the internal periphery of the fluid passages in a particle counting system Such accumulations often result in clogs which impair or impede the passage of sample fluids through the system, resulting in gross miscalculations of particles per unit volume.
Disconnected tubes, faulty seals, and physical breaches in fluid passages can result in leakages that also undermine the accuracy of a particle count. Such leakages are common problems in particle counting systems, and are particularly harmful when small enough to remain substantially undetectable.
If undetected, clogs and leaks can result in numerous harmful errors, particularly in the field of medical diagnostics, where such errors can pose serious health and safety risks to patients, since doctors and other medical personnel rely heavily upon the results of blood cell and other counts in making a medical diagnosis, prescribing medication, and formulating medical strategies for the treatment of all types of injuries and diseases.